Latent and sensible loads in radiant cooling
What Is The Difference Between Latent and Sensible Loads in Radiant Cooling?
However, you may not be completely familiar with what latent and sensible energy are, and what they mean in the context of a radiant cooling system. Therefore, in this short blog, I will cover what the differences between latent and sensible loads in radiant cooling are.
Latent load
Latent energy is the energy absorbed by a system, causing a change in phase, without a change in temperature. For example, the energy added to change water from liquid to gas or vice versa will not change the actual temperature of the water.
Sensible load
Sensible energy is the energy in the system that alters the temperature without a change in phase. For example, adding energy to a pot of water at 10 °C using a stove will cause the water to increase in temperature, without changing to water vapor until it reaches 100 °C.
Latent and sensible loads in radiant cooling
Regarding HVAC, latent energy essentially refers to the relative humidity or moisture in the air. A high latent load would mean that the relative humidity was high.
Sensible energy is the energy that alters the mean radiant temperature (MRT) and air temperature that you can feel. In HVAC it is important to remember that latent and sensible loads interact to affect the operative temperature (overall thermal environment) that occupants experience. For instance, an air temperature of 28 °C at a relative humidity of 20 % (high sensible load, low latent load) would probably feel comfortable.
For radiant cooling systems, both latent and sensible energy are critical concerns.
Firstly, sensible load hugely affects comfort. Both radiant and convective energy transfer that affect operative temperature needs to be accounted for to help regulate thermal comfort.
Secondly, regulating the latent load (i.e. keeping the relative humidity within the desired range of 30 – 65 %) is vital to both occupant health and comfort, but also to the functionality of the radiant cooling system. A dew point higher than the temperature of a radiant cooling surface could risk issues with condensation.
Radiant cooling systems monitor and regulate the MRT as well as the air temperature (often in conjunction with other air temperature control systems). However, radiant cooling systems do not independently control the latent energy load. Radiant cooling systems have to be coupled with systems such as DOAS that control the latent energy load, as well as energy recovery.
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